Thanks for the post#83. The Altec 1590 topology is very similar to my PA/ceiling amps. I'm searching for the best possible modification for the amplifiers and the Altec is perfect if the sound quality is as good as being said.

I see that the circuit is single ended with little bias. But to force linearity it uses rough bias/feedback. Resistor divider networks, too many capacitors in the signal path (to block DC). The result is a highly distorted/noisy amp. The spec says below 1% (which is big). You may say that THD doesn't say much but I'm sure it is audible in this amp (like in mine). My amps are capable of 40Hz, the Altecs are specified 45Hz. I don't think the Altec is high-end, but I hope it is!

No, not in general. The disadvantage is harsh sound in high frequency aera above approxximately 5 KHz. But the advantage is a clear and tight bass transmission. For Tweeters pure class a (at best single ended) is the royal way.

Quote:

Originally Posted by Jay

Hi Tief,

Thanks for the post#83. The Altec 1590 topology is very similar to my PA/ceiling amps. I'm searching for the best possible modification for the amplifiers and the Altec is perfect if the sound quality is as good as being said.
I see that the circuit is single ended with little bias. But to force linearity it uses rough bias/feedback. Resistor divider networks, too many capacitors in the signal path (to block DC). The result is a highly distorted/noisy amp. The spec says below 1% (which is big). You may say that THD doesn't say much but I'm sure it is audible in this amp (like in mine). My amps are capable of 40Hz, the Altecs are specified 45Hz. I don't think the Altec is high-end, but I hope it is!

I haven't heard and investigate the Altec 1590. This means, that it may be quite, that it's sound is very bad through certainly (me unknown) design errors resp. through unwanted parasitic effects.
Please note: If you have found the best possible circuit topology, you don't have automaticly the best sounded amplifier.

I have just followed some links regarding the Altec amp. It is indeed a low-end amp

Quote:

Originally Posted by tiefbassuebertr

The disadvantage is harsh sound in high frequency aera above approxximately 5 KHz. But the advantage is a clear and tight bass transmission. For Tweeters pure class a (at best single ended) is the royal way.

I guess the crossover effect in class-B will be minimized if the voltage transformation is kept low, hence current-driven. Using lateral mosfet and a properly designed speaker (using ultra high frequency tweeter such as the dynaudio) I don't think I have ever needed more in the treble region. The speaker affects the treble more than the amp (speaking of hi-end amps) anyway.

Speaking of the best schematic, I wonder why nobody interested to improve the performance of the Mooly's amplifier. Searching for the most suitable transistors, increasing the slew rate (higher rail, regulated front end), removing the feedback cap, improving linearity, improving power etc.

The key to my amplifier implementations is the choice of the transistors!

There are other reason to get 100W-1000W. Circlomos Isn't classB, and only +/-35V. The difficult things in 100W and up are many things, like thermal, efficiency, component limitations, then how to prevent classB from creating noises when there is any current back from loudspeaker, manage the damper, failure protections, and some more.
Speed and matching devices is not everything (sometimes not needed), single ended classA facing just a current source, and loudspeaker itself is very different between front and back.